Additive manufacturing (aka, 3D printing) is an emerging technology for making a new class of multifunctional nanocomposites for many niche items such as medical implants, and a wide range of industrial designed components. Additive manufacturing technology allows printing complex 3D objects layer-by-layer enabling nanomaterials in new ways toward greater control over material properties across three dimensions and could further extend capabilities of nanocomposites. However, the stability of these materials during the use phase and at the end-of-their useful life is not entirely understood. The potential release of nanomaterials from polymer matrices becomes a concern as a high volume application of additive manufacturing is coming real. It is critically important to understand the relationship between the inherent characteristics of nanocomposite based consumer products and the likelihood of the release of nanomaterials throughout the life-cycle of the product. This research work is focused on weathering of additive manufacturing nanocomposites that contain different weight percentages of carbon nanofiber and carbon nanotubes. Various analytical techniques have been used for the characterization of structural changes and the potential for release of nanomaterials (NMs) from the composite matrix. Structural changes at selected times of the aging process were measured using thermogravimatric analysis and differential scanning calorimetry. The results of this study are essential to develop environmental risk assessment of additive manufactured materials over their life cycles.